Process of eliminating the sulfur from sulfid ores.



Patented Sept. 23,1902.-

. A. GUTENSUHN.

PROCESS OF ELIMINATING THESULFUR FROM SULFID ORES.

(Application filed Feb. 21, 1901.)

(No Model.)

umu. WASHINGTON n c UNITED STATES PATENT OFFICE.

ADOLPII GUTENSOIIN, OF LONDON, ENGLAND, ASSIGNOR TO SULPHUR ELIMINATION SYNDICATE, LIMITED, OF LONDON, ENGLAND.

PROCESSOF ELIMINATING THE SULFUR FROM SULFiD ORES.

SPECIFICATION forming partof Letters Patent No. 709,482, dated September 23, 1902.

Application filed February 21, 1901. Serial No. 48,368. (No specimens.)

To all whom it may concern/.-

&c.--and also from ores in which sulfids may be associated with arsenic, tellurium, or other volatile elements, or from artificial products, such as concentrates or mattes. Where arsenic, tellurium, &c., are present, the substances Will be eliminated with the sulfur. All methods hitherto used demand a prolonged roasting period and a consumption of a considerable proportion of fuel. Moreover, it is always a matter of extreme difficulty by such methods to eliminate the last portions of the sulfur and to obtain a dead or sweet roast. This difficulty is greater still when arsenic, antimony, or tellurium are present, also blende and galena. By this process these difficulties are either entirely avoided or greatly minimized. The roasting period is reduced to a small fraction of the time hitherto required, and the sulfur is'either completely eliminated, if the process is perfect, or if not, left only in small quantities in the form of soluble or insoluble sulfates of the metals present, which will not interfere with subsequent extraction operations for gold or silver.

The accompanying drawing shows a trans verse section of a furnace which may be employed.

According to this invention I mix suitablycrushed iron pyrites', or iron pyrites admixed with other sulfid ores, or sulfid ores without such admixture, with a certain proportion of similarly-powdered carbon or suitable carbonaceous material and add to the mixture or to the carbon, (gZJCr, beforehand a further suitable proportion of sodium sulfid, or a mixture of carbon and sodium sulfate, or sodium carbonate, or sodium hydroxid, or such other suitable salt of sodium, as by interaction with carbon and a metallic sulfid, shall be capable of producing during the first stage of the operation sul fid of sodium. The mixture is then exposed to a low heat-say approaching incipient redness-for a short time. This time will naturally vary according to the richness of the orein sulfur and to the fineness to which it has been ground,and may be from a few minutes. t0,say, half an hour, according to the circumstances of the case. Probably what takes place when the mixture of iron pyrites, sodium sulfid, and carbon are first heated is thatacertain amount of carbon disulfid is formed and also sodium polysulfid and the iron reduced to the state of monosulfid of iron. This may be expressed by the following equation:

(Note, x denoting an excess quantity.) The crystals of FeS thus become broken down and the FeS is left in a minutely-divided condition intimately mingled with finely-divided carbon, which keeps the heated mass in an open porous condition, through which air can freely penetrate. On removing the charge from the source of heat and exposing to air rabbling, if necessary-or by freely admitting air after this first stage of the operation oxidation proceeds with the greatest rapidity, partly by reason of the mass being already heated to a heat approaching incipient redness, partly by reason of its open porous condition, and partly because the carbon itself becomes oxidized and aids in further heating the mass. The mass becomes heated to a red heat, and the carbon and much of the sulfur are burned off, leaving the iron in the form of red oxid (Fe O and the sodium in the form of sulfate, which can readily be removed and allow of gold, silver, 850., being extracted by any suitable means, such as by chlorination, amalgamation, or by cynidation. This may be expressed by the following equation:

To heatthe mixed ore, carbon, and sulfid of sodium before exposing it to air, the mixed mass may be placed in a layer a few inches deep upon a plate heated by a fire below, and a suitable cover should be placed over the plate to more or less exclude air.

In the drawing, A indicates the plate, B the fireplace below it, and O the cover.

When the mass has become sufficiently heated, the cover may be removed and the mass raked oif and exposed to air and rabbled to allow of its oxidation, or it may be allowed to oxidize on the plate, or the preliminary heating might be effected in other forms of furnace in a neutral or reducing flame and subsequently oxidized, or the heating and oxidation may be carried on continuously.

I find that pyrites or mispickel charges which hitherto would have required a calcination period of many hours, even in some cases up to twenty-four hours, can when heated in the manner above described be freed from sulfur and brought to the state of a dead or sweet roast after a period of from, say, one hour to two hours in the furnace, the completion of the oxidation being effected by exposure to the open air.

In view of the wide variations in composition of the ores before mentioned it is not easy to give definite proportions of the materials to be used in every case; but I have found a useful admixture to be the following: Powdered carbon equal to about one-fifth of the total sulfur present with the addition of a suitable sodium saltsay of dry sulfid of sodium (Na S)which shall be equivalent to about one-fifth of the weight of carbon, or, if a mother-liquor of sodium sulfid crystals be employed, a weight of this equal to half the carbon used. After the reaction is complete the sodium will be found to be present as sodium sulfate, while the carbon has nearly or entirely disappeared. This reaction has the further advantage that it can be used with great efficiencyin producing what is known as a chloridizing roast'. This operation is frequently employed in the treatment of ores which contain sulfid, antimonid, &c., of silver associated with other metallic sulfids. If such an ore be roasted in the ordinary way, with the addition of the requisite quantity of sodium chlorid, the silver is found in the form of chlorid at the end of the roasting operation. The degree of heat and the length of time, however, required under such cir-,

cumstances give rise to considerable losses of the precious metals as volatilized chlorids, whereas the low temperature and the short period required by my method avoids these serious chloridizing losses. The sodium chlorid required may be added before the commencement of the roast or at any stage prior to the final breaking up of the sulfates.

I do not necessarily bind myself to the proportions given, as it will ,be evident that a certain minimum proportion of carbon is required even in ores very poor in sulfur, but state the above as an example of the admixture which I have found to be efficacious in the treatment of rich pyritic and arsenical gold ores and concentrates. The gold and silver can be extracted from the residues by any suitable means, such as by chlorination, amalgamation, cyanidation, &c.

What I claim is 1. The hereinbefore-described process for the elimination of sulfur from sulfid ores, consisting in crushing the ore, mixing it with carbon and a sodium salt which will yield sulfid of sodium when the mixture is heated, the amount of carbon added being largely in excess of the amount required to form the sulfid of sodium heating the mixture to a temperature approaching incipient redness, and then exposing it freely to air to elfect its oxidation and burn off all sulfur that is set free.

2. The hereinbefore-described process for the elimination of sulfur from sulfid ores, consisting in crushing the ore, mixing it with carbon and sodium sulfid, heating the mixture to a temperature approaching incipient redness, and then exposing it freely to air to effect its oxidation and burn off all sulfur that is set free.

3. The hereinbefore-described process for the elimination of sulfur from sulfid ores, consisting in crushing the ore, mixing it with crushed iron pyrites, carbon and a sodium salt which will yield sulfid of sodium when the mixture is heated, the amount of carbon added being largely in excess of the amount required to form the sulfid of sodium heating the mixture to a temperature approaching incipient redness, and then exposing it freely to air to efiect its oxidation and burn off all sulfur that is set free.

4. The hereinbefore-described process for the elimination of sulfur from sulfid ores, consisting incrushing the ore, mixing it with crushed iron pyrites, carbon and sodium sulfid, heating the mixture to a temperature approaching incipient redness, and then exposing it freely to air to efiect its oxidation and burn off all sulfur that is set free.

5. The hereinbefore-described process for the elimination of sulfurfrom sulfid ores, consistingin crushing the ore, mixing it with carbon, sodium chlorid and a sodium salt which will yield sulfid of sodium when the mixture is heated, the amount of carbon added being largely in excess of the amount required to form the sulfid of sodium, heating the mixture to a temperature approaching incipient redness, and then exposing it freely to air to effect its oxidation and burn off all sulfur that is set free.

6. The hereinbefore-described process for the elimination of sulfur from sulfid ores, consisting in crushing the ore, mixing it with carbon, sodium chlorid and sodium sulfid, heating the mixture to a temperature approaching incipient redness, and then exposing it freely to air to effect itsoxidation and burn oif all sulfur that is set free.

7. The hereinbefore-described process for the elimination of sulfurfrom sulfid ores, consisting in crushing the ore, mixing it with crushed iron pyrites, carbon, sodium chlorid and a sodium salt which will yield sulfid of sodium when themixture is heated, the amount of carbon added being largely in excess of:

the amount required to form the sulfid of sodium, heating the mixture to a temperature approaching incipient redness, and then exposing itfreely to air to eifect its oxidation and burn off all sulfur that is set free.

8. The hereinbefore-described process for the elimination of sulfur from sulfid ores, conassisting in crushing the ore, mixing it with a crushed iron pyrites, carbon, sodium, chlorid,

and sodium sulfid, heating the mixture to a temperature approaching incipient redness, andthen exposing it freely toair to effect its oxidation and burn off all sulfur that is set free. i

i i 9. The hereinhefore-described process for the elimination of sulfur from sulfid ores, consisting in crushing the ore, mixing it with care hon and a sodium salt which will yield sulfid of sodium when the mixture is heated, the amountof carbon added beinglargelyin excess of the amountrequired to form the sulfid of sodium, heating the mixture to a temperature approachingincipient redness,adding sodium chlorid during the heating, and then exposing it freely to air to effect its oxidation and burnoff all sulfur that is set free.

10. The hereinbeforedescribed process for the elimination of sulfurfrom sulfid ores, consisting in crushing the ore, mixing it with carbon and sodium sulfid, heating the mixture to a temperature approaching incipient redness, adding sodium chlorid during the heating, and then exposing it freely to air to effect its oxidation and burn off all sulfur that is set free.

11. The hereinbefore-described process for the elimination of sulfur from sulfid ores, consisting in crushing the ore, mixing it with crushed iron pyrites, carbon and a sodium saltwhich will yield sulfid of sodium when the mixture is heated, the amount of carbon added being largely in excess of the amount required to form the sulfid of sodium, heating the mixture to a temperatureapproaching incipient redness, adding sodium chlorid during the heating, and then exposing it freely to air to effect its oxidation and burn ofi all sulfur that is set free.

12. The hereinbefore-described process for the elimination of sulfur from sulfid ores, con- 

